This invention relates to a magnetic recording and reproducing device of the helical scan type, and more particularly to a magnetic recording and reproducing device having a rotary drum construction wherein reproduction monitoring can be made simultaneously with recording.
In a magnetic recording and reproducing device of the helical scan type such as a VTR (video tape recorder) or a DAT (digital audio tape recorder), a magnetic tape is fed while being wrapped over 180 degrees or more in the case of a VTR or over 90 degrees or more in the case of a DAT around an outer periphery of a head cylinder composed of a fixed drum and a rotary drum on which a magnetic head is carried while an information signal such as a video signal or a digital audio signal is recorded on or reproduced from the magnetic tape.
Similar to a tape deck of the analog type, it would be desirable for such a magnetic recording and reproducing device to have a simultaneous recording and reproduction monitoring function which enables confirmation of recording. To this end, it may be recommended to provide a recording magnetic head and a reproducing magnetic head separately on a rotary drum (for example, U.S. Pat. No. 4,628,373).
A rotary transformer is provided for electrically connecting magnetic heads on a rotary drum to signal processing circuits. The rotary transformer includes a winding provided for each of the magnetic heads (such a winding will be hereinafter referred to as a "channel"). Since at least two recording magnetic heads and two reproducing magnetic heads are required, a total of four channels including two recording channels and two reproducing channels must be provided.
If at least four channels are provided on a rotary transformer in this manner, crosstalk between the channels, particularly between the recording channels and the reproducing channels, becomes an issue, and reproduction monitoring which is conducted simultaneously with recording may be hindered.
To avoid this problem, steps have been taken such as providing a short ring between adjacent channels or to dividing the rotary transformer at least for the recording channels and the reproducing channels. However, this will narrow a magnetic path at each channel of the rotary transformer, which will result in reduction in the degree of coupling and an increase in transmission loss of a signal. This is a serious problem particularly with the reproducing channels because a signal reproduced from a magnetic tape is a feeble signal.
In order to resolve the problem, it is necessary to widen the magnetic path for each reproducing channel. To this end, however, the diameter of the rotary transformer must be increased, which will increase the overall size of the rotary transformer. Further, since the rotary transformer is disposed within a head drum, if the size of the rotary drum is increased, then the overall size of the head drum is increased, which will result in an increase in the overall size of the magnetic recording and reproducing device and an increase in the cost of the device.
Due to such circumstances as described above, conventional magnetic recording and reproducing devices are not provided with a simultaneous recording and reproduction monitoring function.